The new prime minister finds himself under an uncomfortable spotlight

IT WAS Saturday evening and Yukio Hatoyama, wearing a burgundy jacket and a cocky grin, was dancing with his fun-loving wife under the bright lights of a charity fashion-show. He could not have looked less like the “grim-faced prime minister”, who hours earlier had been ambushed outside his home by reporters asking about his role in a fund-raising scandal.

He will need to keep up the brave face for several months yet. Just weeks after leading his party to an historic change of regime, Mr Hatoyama finds his campaign-finance activities under scrutiny by a dogged justice system. Prosecutors in Tokyo have given themselves until the end of the year to decide whether to press charges.

Mr Hatoyama can be under no illusion about the seriousness of the issue. He was, in effect, an accidental candidate in the August 30th election. A fund-raising scandal forced the resignation of his predecessor, Ichiro Ozawa. Mr Hatoyama's Democratic Party of Japan (DPJ) won the election by a landslide, evicting the Liberal Democratic Party (LDP), which had held power in Japan almost without interruption since 1955. One of the DPJ's main campaign pledges was for cleaner government.

Shortly before campaigning began, however, Mr Hatoyama had admitted that his political fund-raising organisation, named after yuai, the odd mixture of love and fraternity that is the keynote of his personal philosophy, had about 90 fictitious names, including those of dead people, on its donors' list. They were supposed to have given almost ¥22m ($220,000) from 2005-08. Newspapers reported that his organisation also received certificates enabling the supposed donors to deduct the contributions from their taxes.

Mr Hatoyama, whose family is so fabulously rich that his mother has helped bankroll his political career, blamed a longstanding employee for sloppy book-keeping. The issue went quiet during the election, but this week Mr Hatoyama confirmed that prosecutors had revived the investigation, and said he would co-operate fully. Prosecutors had summoned some of the donors named on his list for questioning.

Some commentators suggest that the irregularities may have stemmed in part from embarrassment at the extent of his own family's contributions, and may not be viewed too harshly. In a poll this week by Yomiuri Shimbun, Japan's biggest-selling newspaper (which has pro-LDP leanings), 71% of respondents supported Mr Hatoyama's cabinet. Yet, coincidentally, the same percentage were unconvinced by his explanation about the case.

If tax fraud is suspected, the case could be very “dangerous” for Mr Hatoyama and the DPJ, says Jiro Yamaguchi of Hokkaido University, who has worked as an adviser to the party. “I hope it will blow out, but I think this could develop into a big money scandal.” It is also likely to prove a godsend for the LDP after its election rout. It is trying to revive itself under the new leadership of 64-year-old Sadakazu Tanigaki, an uninspiring former finance minister. The LDP was wracked by further despair this week when Shoichi Nakagawa, another ex-finance minister, was found dead at his home on October 4th. He was fired from the previous government after appearing to be drunk while giving a press conference at the G7 in Rome in February.

The attention on Mr Hatoyama could raise the pressure for campaign-finance reform in Japan. The DPJ hopes to revive a bill it submitted in June that would ban political donations by corporations, unions and other groups. Its motive is easy to understand: businesses provided the party with just ¥120m in 2008, compared with a whopping ¥2.9 billion for the LDP. But the success or failure of its reform efforts may depend on whether this is a scandal that Mr Hatoyama can dance around.